将一个正整数分解质因数。例如：输入90,打印出90=2*3*3*5。

程序分析：对n进行分解质因数，应先找到一个最小的质数k，然后按下述步骤完成：

(1)如果这个质数恰等于n，则说明分解质因数的过程已经结束，打印出即可。

(2)如果n <> k，但n能被k整除，则应打印出k的值，并用n除以k的商,作为新的正整数你,重复执行第一步。

(3)如果n不能被k整除，则用k+1作为k的值,重复执行第一步。

-The prime factorization of a positive integer. For example: Enter 90, print out 90 = 2* 3* 3* 5. Program analysis: the decomposition n prime factors, you should first find a smallest prime number k, then complete the following steps: (1) if the prime exactly equal to n, then the prime factor decomposition process has been completed, you can print out . (2) If n < >　k, k but can be divisible by n, the value of k should be printed, and the quotient k divided by n, a positive integer as a new you repeat the first step. (3) If n is not divisible by k, the value of k is used as k+1 Repeat the first step.